BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to mixtures oi halogenated alkyl phosphate esters containing
aliphatic bromine and chlorine which may be used to flame-retard polymeric systems
such as flexible polyurethanes, reaction injection molded polyurethanes, polyvinyl
chloride, textile fibers, and poly-(methylmethacrylate), and the like.
2. Description of the Prior Art
[0002] The need to reduce the flammability of polymeric systems while not adversely affecting
the chemical, physical and mechanical properties or the appearance of polymeric systems
is disclosed in the Encyclopedia of Polymer Science and Technology, Volume 7, pp.
1-3 and The Encyclopedia of Chemical Technology, 3rd Edition, Volume 10, pg. 348.
[0003] Phosphorous-halogen systems have been widely used to flame retard polymeric systems.
For example, the use of certain pentavalent phosphate esters containing bromine and
chlorine as flame retardants is taught by Birum, et al., U.S. Patent No. 3,132,169.
The compounds of Birum are selected from the general formula: x
wherein
R is selected from the class consisting of hydrogen, alkyl and haloalkyl radicals of
from 1 to 2 carbon atoms,
R' is selected from the class consisting of hydrogen, alkyl and haloalkyl radicals
of from 1 to 5 carbon atoms, R" is selected from the class consisting of R' and hydrocarbyl-
oxymethyl radicals of from 1 to 8 carbon atoms, wherein one R" at a pair of adjacent
carbon atoms must be hydrogen, and n is an integer from 0 to 1.
[0004] Other patents disclosing halogenated phosphate esters include Birum U.S. Patents
Nos. 3,192,242 and 3,344,112; Carpenter U.S. Patent No. 3,324,205; Jenkner et al.
U.S. Patent 3,781,388; Dow et al. U.S. Patent No. 3,830,886; Wilkinson U.S. Patent
No. 3,997,449; Stanaback U.S. Patent No. 4,046,719; Albright U.S. Patent
Nos. 4,083,826 and 4,240,953; and West German OS 2,416,663.
Applicants' own U.S. Patent No. 4,083,825 discloses the use of bis(2-chloroethyl) 2,2-dimethyl-3-bromopropyl
phosphate as a flame retardant for polyurethane foams.
[0005] None of the foregoing halogenated alkyl phosphate esters are believed to perform
as effectively as desired as flame retardant additives. Furthermore, numerous halogenated
alkyl phosphates containing aliphatic bromine have been determined to be mutagenic
by the Ames test. On April 28, 1977, the Consumer Products Safety Commission, acting
under the Federal Hazardous Substances Act, banned the sales of children's sleepwear
treated with the flame-retardant tris-(2,3-dibromopropyl) phosphate ("Tris"). In explaining
this action, the Commission cited the two-year feeding test by the National Cancer
Institute that linked Tris to kidney cancer in mice and rats. It also cited studies
showing that Tris, when tested in the Ames Test, was mutagenic in bacteria and, thus,
possibly carcinogenic in humans.
[0006] It is, thus, a primary object of this invention to provide highly effective flame
retardant mixtures of halogenated alkyl phosphates.
[0007] It is another object of the present invention to provide a mixture of halogenated
alkyl phosphate esters containing aliphatic bromine which are not mutagenic by the
Ames Test.
[0008] It is also an object of the present invention to provide effectively flame-retarded
polymeric systems which do not possess any undesirable chemical, physical and mechanical
properties and whose appearance is substantially unchanged by the flame retardant
that is employed.
SUMMARY OF THE INVENTION
[0010] This invention further includes novel methods of preparing such mixtures by reacting
neopentyl glycol with phosphorous trichloride, the resulting intermediate then being
reacted first with bromine to form a halogenated phosphorous monoester and, thereafter,
with ethylene oxide to yield the desired mixture of compounds, which is then then
isolated from the reaction mixture, purified and stabilized.
[0011] The invention also comprises flame retarded polymer systems incorporating effective
amounts of the mixtures of this invention, such polymer systems including flexible
polyurethanes, reaction injection molded polyurethanes, polyvinyl chloride, textile
fibers, poly-(methyl) (methacrylate) , and the like.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Flame-retardant halogenated alkyl phosphate esters of this invention which have improved
flame retarding efficiency and are not mutagenic by the Ames Test comprise a mixture
consisting essentially of compounds of the formula:
Most desirably, Compounds (I), (II), and (III) are present in the mixture in a VPC
area ratio of about 1.0:1.5:1.0.
[0013] The invention mixture of these compounds may be prepared by reacting phosphorous
trichloride with neopentyl glycol to form a cyclic phosphorous compound of the formula:
The cyclic phosphorous compound is then reacted with bromine to cleave the cyclic
structure and produce a ring-opened halogenated phosphorous monoester of the formula:
The ring-opened halogenated phosphorous monoester is then reacted with ethylene oxide
to form the mixture of compounds of the present invention:
The mixture is then isolated, purified and stabilized.
[0014] The foregoing reactions generally proceed quite readily and usually no special reaction
conditions or chemical processing equipment need be employed. These reactions can
be conducted at room temperature, at temperatures above ambient, or at temperatures
below ambient. Elevated temperatures may be used to ensure completion of the reaction,
although some of the foregoing condition reactions are quite exothermic, and it may
be advisable, at least initially, to provide external cooling. It may be preferable,
although not essential, to employ solvents such as halogenated hydrocarbon solvents
(e.g., methylene chloride and chlorobenzene).
[0015] While the presence of a catalyst is generally not required, catalysts may decrease
reaction times and allow the use of lower reaction temperatures. In particular, the
final step of reacting the halogenated phosphorous monoester with ethylene oxide is
facilitated by using a small but catalytically effective amount of titanium tetrachloride
or other catalysts such as tin tetrachloride or magnesium chloride.
[0016] After the halogenated phosphorous monoester is completely reacted with ethylene oxide
to form the mixture of this invention, the mixture is then isolated, purified and
stabilized. Isolation and purification may be carried out by washing with water, aqueous
ammonia or the like, adjusting the pH to a consistent value in the range of about
9-10 and separating and recovering the low viscosity liquid product mixture by phase
separation and filtration.
[0017] Advantageously, the product mixture is acid stabilized by adding a small but effective
amount (e.g., about 0.1 - 5.0 weight percent, preferably about 0.5 - 2.0%) of an acid
stabilizer such as ERL-4221, a cycloaliphatic expoxide commercially available from
Union Carbide Corporation. Other acid stabilizers such as epoxidized soybean oil,
phenyl glycidyl ether, epibromohydrin, and the diglycidyl ether of tetrabromobisphenol
A may also be used.
[0018] The following examples are provided for the purpose of further illustration of the
preferred embodiments of the present invention and are not intended to be limitations
on the disclosed invention.
EXAMPLE 1
[0019] To 142.82 g. (1.04 mole) of phosphorous trichloride, a solution of 104.1 g. 1.00
mole) neopentyl glycol and 188 ml. of methylene chloride maintained at 38°C., was
added dropwise while the reaction mixture was maintained at or below 10°C. Once the
addition was complete, the reaction mixture was heated to 30°C. and maintained at
this temperature for one-half hour. The methylene chloride was then removed from the
reaction mixture under aspirator vacuum. After cooling the reaction mixture to 20
oC., 160 g. of bromine (1.00 mole) was added while the reaction temperature was maintained
below 20°C. with the cooling. Titanium tetrachloride catalyst, 1.9 g. (0.01 mole)
was then added, and ethylene oxide addition started immediately. The reaction temperature
was maintained below 65°C and ethylene oxide addition continued until the exothermic
reaction subsided. A total of 165.8 g. (3.8 mole) ethylene oxide was added. The product
was washed with aqueous ammonia and then separated from the aqueous layer. After vacuum
drying, one percent by weight of ERL-4221 as an acid stabilizer was added to the product
and thoroughly mixed. The product yield was 98% based on neopentyl glycol.
[0020] Analysis of the unstabilized product shows: 37.82% bromine (38.4% theor.); 8.13%
chlorine (8.5% theor); 0.2% water; acid no. 0.01 milligrams KOH per gram. Analysis
of the product by vapor phase chromatopography area analysis showed that three primary
components were present.
The ratio of the three compounds (I):(II):(III) in this product was found be about
1.0 to about 1.5 to about 1.0 as determined by VPC area analysis.
EXAMPLE 2
[0021] To 145.6 g. (1.06 mole) of phosphorous trichloride cooled to 5°C, 104.1 g. (1.00
mole) of neopentyl glycol (solid) was added at an even rate so that the reaction temperature
was maintained below 7°C. Once the addition was complete, the reaction mixture was
held below 7
0C for 60 minutes. The reaction mixture was then heated to 30°C for 30 minutes and
finally vacuum stripped at 30°C for 30 . minutes. Bromine 159.8 g., (1.00 mole) was
then added while the reaction mixture was held below 30°C. Next, the mixture was heated
to 50°C and vacuum stripped for 30 minutes. After cooling to ambient temperature,
1.9 g. (0.01 mole) of titanium tetrachloride was added, and 98.7 g. (2.24 mole) ethylene
oxide was added subsurface while the reaction temperature was held below 85°C with
cooling. The reaction mixture was then held at 85
0C for 30 minutes. After cooling, the product was washed with aqueous ammonia and then
separated from the aqueous layer. After vacuum drying, one percent by weight of ERL-4221
as an acid stabilizer was added to the product and thoroughly mixed. The product yield
was 95% based on neopentyl glycol. Analysis of the unstabilized product shows: 37.2%
bromine (38.4% theor.); 8.3% chlorine (8.5% theor.); 0.1% water; acid no. 0.04 milligrams
KOH per gram. Distribution of compounds in the product mixture was: 1.0:1.5:0.9 (I:III:III),
as determined by VPC area analysis.
EXAMPLE 3
Mutagenicity Testing
[0022] Three different samples of phosphate mixtures prepared in accordance with Example
1 were tested for mutagenic activity in a series of in vitro microbial assays employing
Salmonella indicator organisms. Also, one such sample was tested for mutagenicity
in the in vitro transformation of BALB 3T3 by the technique well known to those skilled
in the art. When tested in this manner, the phosphate mixture of the present invention
did not exhibit genetic activity in any of the assays conducted, nor was it mutagenic
under these test conditions. (See Ames, B. N. McCann, J. and Yamasaki, E., "Methods
for Detecting Carcinogens and Mutagens with the Salmonella/Mammalian-Microsome Mutagenicity
Test" Mutation Research, 31, 347-64 (1975)). This result was most surprising because
a number of related halogenated phosphates have been studied and found to be mutagenic
by the Ames Test. Compounds in this class include bis(2,3-dibromopropyl) 2,2-bis(bromomethyl)-3-chloropropyl
phosphate, which is specifically disclosed in Example 2 in U.S. Pat. 4,240,953. Moreover,
3-bromo-2,2-dimethylpropyl 1-bromo-2-propyl 1-chloro-2-propyl phosphate, disclosed
in Example 2 of Birum U.S. Patent No. 3,132,169, has also been found to be mutagenic
to strain TA1535 in activation assays. And, 3-bromo-2, 2-dimethylpropyl 1-bromo-3-chloro-2-propyl
l,3-dichloro-2-propyl phosphate disclosed in Applicant's U.S. Pat.
4,083,825 has been evaluated and, likewise, shown to be mutagenic.
. APPLICATIONS
[0023] The halogenated alkyl phosphate mixtures of the present invention may be used as
flame retardants in a wide variety of natural and synthetic polymeric systems including
amino resins, cellulose acetate, epoxy resins, acrylic latexes, SBR Rubber, vinyl
acetate latexes, nitrocellulose lacquer, paper, phenolic resins, unsaturated polyester,
poly-(methylmethacrylate), nitrile rubber, urethane coatings, flexible polyvinyl chloride,
flexible polyurethane foam, bonded polyurethane foam, rigid polyurethane foam, reaction
injection molded ("RIM") polyurethanes, polystyrene foam, fabric containing formulations,
and wood.
[0024] The flame retardant mixture of this invention may be incorporated into or applied
onto virtually any flammable polymeric material by techniques which are standard or
known to those skilled in the art. See, for example, J.M. Lyons, "The Chemistry and
Uses of Fire Retardants", Wiley-Interscience, New York, NY (1970), and Z.E. Jolles,
"Bromine and Its Compounds", Academic Press, New York, NY (1966).
[0025] Depending on the substrate and the amount of flame retardancy desired, up to about
40 weight percent of the flame retardant mixture may be incorporated therewith. However,
in most applications, it is preferred to use less than 25 weight percent of compounds
within the scope of this invention. It should be noted that the optimum level of additive
of the flame retardant mixture within the scope of this invention depends upon the
particular substrate being treated as well as the level of flame retardancy desired.
For example, in polyurethanes, a flame retardant level of from about 0.5 - 12 percent
by weight of the total polymeric composition is satisfactory.
[0026] It is to be understood that the term polyurethanes as used herein means polymers
containing repeated urethane linkages:
where R is an aromatic or aliphatic group. These polymers are generally made by reacting
a polyisocyanate with a compound having a plurality of hydroxyl groups..
[0027] Thus the polyurethanes used in the present invention compositions are any polyurethane
herein defined and which one so desires to flame retard,. It is to be understood that
the polyurethanes used can be a "virgin" material, i.e., substantially free of additives
such as stabilizers, platicizers, dyes, pigments, fillers, and the like, or the polyurethanes
can have additives (such as those mentioned and described herein) already contained
therein or added concurrently with or after the addition of the phosphate compounds
of formula I. These polyurethane compositions include: rigid foams, semi-rigid foams,
flexible foams, rubbers and adhesives.
[0028] The phosphate mixtures of this invention are particularly effective in flexible polyurethane
foams and RIM polyurethane.
[0029] It is also within the scope of the present invention to employ other materials in
the present invention compositions where one so desires to achieve a particular end
result. Such materials include, without limitation, adhesion promotors; antioxidants;
antistatic agents; antimicrobials; colorants; plasticizers, etc., such as those listed
on pages 594-655; Modern Plastics Encyclopedia, 1984-1985; (in addition to the new
class of flame retardants described herein); heat stabilizers; light stabilizers,
pigments; plasticizers; preservatives; ultraviolet stabilizers and fillers. In this
latter category, i.e., fillers, there can be mentioned without limitation, materials
such as glass, carbon, cellulosic fillers (wood flour, cork, and shell flour); calcium
carbonate (chalk, limestone, and preciptated calcium carbonate); metal flakes; metallic
oxides (aluminum, beryllium oxide and magnesia); metallic powders (aluminum, bronze,
lead, stainless steel and zinc); polymers (comminuted polymers and elastomerplastic
blends); silica products (diatomaceous earth, novaculite, quartz, sand, tripoli, fumed
colloidal silica, silica aerogel, wet process silica); silicates (asbestos, kaolimite,
mica, nepheline syenite, talc, wollastonite, aluminum silicate and calcium silicate);
and inorganic compounds such as barium ferrite, barium sulfate, molybdenum disulfide
and silicon carbide.
[0030] The above mentioned materials including filler, are more fully described in Modern
Plastics Encyclopedia, ibid., and which publication has been incorporated herein in
toto by reference.
[0031] The amount of the above described materials employed in the present invention compositions
can be any quantity which will not substantially adversely affect the desired results
derived from the present invention compositions. Thus, the amount used can be any
amount up to that percent based on the total weight of the composition at which said
composition can still be classified as a plastic. In general, such amount will be
from about 0% to about 75% and more specifically from about 1% to about 50%.
[0032] For a detailed description of various polyurethane preparations of specific elastomers
and specific rigid and flexible foams, one is directed to the literature and patents
wherein may be found numerous such detailed descriptions, e.g., K.C. Frisch and J.H.
Saunders, "Plastic Foams", Vol 1, parts 1 and 2, Marcel Dekker, Inc., New York, NY,
1972 and T.H. Ferrigno, "Rigid Plastics Foams", Second Edition, Reinhold Publishing
Corp., New York, 1967.
[0033] The following examples are provided for the purpose of further illustration of polymer
applications employing the mixtures of this invention.
EXAMPLE 4
Polyurethane Foams for Automotive Applications
[0034] Polyurethane foams were prepared using a conventional one-shot process employing
the invention mixture of Example 1 and, for comparative purposes, tris(1,3 dichloro-
isopropyl) phosphate using the following formulation:
[0035] As the foregoing data demonstrate, the mixture of this invention was found to be
significantly more efficient than another halogenated aliphatic phosphate under similar
conditions.
EXAMPLE 5
Polyurethane Foams for Automotive Applications
[0036] Polyurethane foam samples were prepared using a conventional one-shot process employing
the following formulation using the invention mixture (Example 1) and, for comparative
purposes, bis(2-chloroethyl) 2,2-dimethyl-3-chloropropyl phosphate:
[0037] As the foregoing data demonstrate, the mixture of this invention is a significantly
more effective flame retardant than the prior art fully chlorinated analog.
EXAMPLE 6
Polyurethane Foam For Furniture Application
[0038] Foams were again prepared using a conventional one-shot process employing the formulations
given below. In addition to the invention mixture (Example 1), foams were prepared
for comparative purposes using Compound I, the prior art bis(2-chloroethyl)2,2-dimethyl-3-bromopropyl
phosphate of Applicant's U.S. Patent No. 4,083,825, and a commercially available pentabromodiphenyl
ether/aromatic phosphate blend.
[0039] As these data demonstrate, the mixture of this invention was found to be more effective
than Compound I and another commercially used flame retardant when tested under similar
conditions.
EXAMPLE 7
Reaction Injection Molded Polyurethane
[0040] Flame retardant was added to the B Component of
Mobay Baydur 730 reaction injection molding polyurethane resin. A half-inch thick plaque
of this material having an overall density of 37 lb./ft
3 was prepared. Half-inch by half-inch specimens met the UL-94 flammability test V-0
requirement with a flame retardant content of 15% as shown by the data in Table IV.
EXAMPLE 8
Use as a Secondary Plasticizer
[0041] Polyvinyl chloride was compounded with a series of primary and secondary plasticizers,
including the Invention Mixture of Example 1, on a two-roll mill to an even thickness
sheet from which a series test specimens were cut or stamped. The basic formulation
is given in Table V.
[0042] A total plasticizer level of 60 parts was maintained. Composition, tensile data,
and oxygen indices (a measure of flame retardancy) are given in Table VI.
[0043] As these data demonstrate, the mixture of this invention performs adequately as a
secondary plasticizer while greatly enhancing flammability test performance.
EXAMPLE 9
Use As a Flame Retardant for Textile Fibers
[0044] A woven 100% polyester fabric weighing approximately 5 oz./yd
2 was backcoated with the composition given in Table VII.
[0045] A knife blade was used to achieve a.uniform coating thickness. Upon drying, the flame
retardant comprised 10% of the total weight (fabric and backcoating). The backcoated
fabric met the flammability criteria of Motor Vehicle Safety Standard 302.
EXAMPLE 10
Use as a Flame Retardant for Poly(Methyl) (Methacrylate)
[0046] Forty grams Rohm and Haas Plexiglas V-920 poly-(methylmethacrylate) was processed
at 200°C. and 75 rpm for 10 minutes in a Brabender Plasticorder. A total of 7.2 grams
Invention Mixture (Example 1) and tris(dibromopropyl) phosphate were respectively
added slowly to separate samples during the first five minutes. The compounded plastics
were pressed to 1/8" thickness for five minutes at 350°F. Upon cooling the plaques
were cut into specimens for flammability testing. PMMA containing Invention Mixture
and tris-(dibromopropyl) phosphate each met UL-94 V-2 requirements.